This invention relates to apparatus that has a wide range of applications and that is especially adapted for use in dentistry. More particularly, it relates to a novel and highly effective "fluidic block" whereby many power and control functions that have heretofore required bulky, expensive, and complicated equipment can be performed by equipment that is compact, inexpensive and simple.
Modern dentistry requires the use of power tools such as high-speed drills that have the capability of drilling with or without the addition of water, that can be closely controlled as to drill speed and water flow, and that are easy for a dentist to use. Much progress has been made towards providing such tools, including the improvements disclosed in the applicant's prior U.S. Pat. No. 4,069,587.
That patent discloses an arrangement whereby removal of a dental handpiece or tool from its holder coupled with operation of a pedal valve opens a pilot-operated main valve for supplying air or both air and water to the handpiece. The patent discloses several arrangements. In one, there are aligned, narrow air passages on opposite sides of a recess which receives the handpiece, and the handpiece blocks these passages when it is in the holder. Upon removal of the handpiece, the flow of air from one of these passages across the recess and into the the passage supplies pilot pressure enabling opening of the pilot-operated main valve.
The prior structure includes a composite valve that serves both as a main valve for enabling or blocking flow of air to the drill and as the pilot valve for controlling the operation of the main valve. This structure does not lend itself to miniaturization or to the most efficient mass production.